Accumulator or pulsation dampener



United States Patent A'CCUMULATOR on PULSATION DAMPENER Granville S. Knox, Glendale, Calif., assignor to Hydril Company, Los Angeles, Calif., a corporation of Ohio Application December 22, 1952, Serial No. 327,280

3 Claims. (Cl. 138-30) This invention has to do generally with accumulators or pulsation dampeners, but it will suflice to discuss the nature and operation of the device solely as a pulsation dampener, without thereby implying that its adaptation is limited to such service.

The invention is particularly well adapted to handle the severe service requirements of and to withstand the severe conditions encountered in pumping mud laden fluid during well drilling operations, and therefore I have illustrated and will describe an embodiment especially suited to that use, though this is not to be construed as limitative.

In the above environment, the dampeners are installed in output lines of reciprocating-plunger, mud or slush pumps, to smooth out pressure peaks. The pre-charged surge chamber effectively eliminatessurging and water hammer in the rotary hose and mud lines, resulting in longer service life and less maintenance trouble and expense as regards the pumps, the rotary hose, the swivel packing, etc-all as is well understood in the art.

It is among the objects of the invention to provide a simple, durable dampener which has maximum surgecharnber capacity in spite of its relatively small over-all size, there being no dead space within the device. A special object of the invention is to so shape the chamber and diaphragm that the diaphragm not only performs in a particularly efiicient manner, but is adapted to have exceedingly long life in spite of constant flexing. The arrangement is such that harmful folding, wrinkling and stretching of the diaphragm are reduced to a minimum in spite of the relatively long stroke of the diaphragm. Moreover, when the time comes for diaphragm inspection or replacement, it is an easy operation to withdraw, inspect and replace the diaphragm, or to substitute a new diaphragm.

It is a still further object of the invention to render the device self-cleaning; that is, when the pumps are shut down, the gas pressure above the flexible diaphragm may be utilized to force that member downward to effect displacement of mud laden fluid through an unobstructed outlet in the lower part of the body. This prevents an undue accumulation of sediment in the body chamber and insures maximum operating efliciency at all times.

On the other hand, there is provision for trapping a limited amount of fluid between the shell wall and the flexing portion of the diaphragm to prevent abrasive Wear on the diaphragm. Certain parts of the device are so shaped that the sediment entering the chamber is evenly distributed to the extent that there are no harmful local accumulations during operation.

I have also provided a novel and particularly eflicient valve stopper which closes the surge passageway when the diaphragm is fully distended, preventing extrusion of the diaphragm into that passageway.

Other objects and features of the invention will become apparent from the following detailed description, reference being bad to the accompanying drawings, in which,

Fig l is a side elevation of the dampener;

2,757,689 Patented Aug. 7, 1956 Fig. 2 is a top plan view of Fig. l; and

Fig. 3 is an enlarged section on line 3-3 of Fig. 2.

The body shell 10 is made up of a main section 11, cap section 12, and bottom section 13. The portions of the shell above and below the central axial plane A will be considered, respectively, as upper and lower shellwalls 14 and 15. The upper end of section 11 has a relatively large, central mouth 16 which receives the cylindrical plug portion 17 ofsection 12, while the flange portion 18 of section 12 is bolted to section 11 at 19. The peripheral face 20 of plug portion 17 is annularly spaced from the defining wall 21 of mouth 16 to provide a downwardly opening, annular groove 22 which, as well as counter-bore 23, serve to receive portions of the diaphragm, as will later appear.

The lower end of section 11 has a relatively small, central mouth 24 adapted to receive the cylindrical plug portion 25 of bottom section 13, the flange portion 26 of section 13 being bolted to section 11 at 27. The joint between sections 11 and 13 is packed olf by compressed sealing ring 28. Flange 26 has threaded holes 29 to receive bolts 30 (Fig. 1) whereby the flange 31 of fitting 32 may be fastened to the dampener, this fitting. being connected by pipe 32 to the output line (not shown) of a pump or the like. The pipe communicates with the central flow passage 33, of which more will be said later, extending through bottom section 13.

Walls 14, 15 define a chamber C which has the general shape-characteristics of an oblate spheroid with its polar or shorter axis B extending vertically, it being understood that the words vertical and horizontal are used in this description and in the claims merely for the purpose of relative orientation of parts and not in their limited sense. Axial plane A may thus be considered as the equatorial axial plane of chamber C, since the line representing that plane also represents the longer axis of the generating ellipse. I

The lower portion of the defining wall of chamber C is preferably slightly modified so that the curved defining wall 34 merges smoothly into a conical surface or zone 34 immediately surrounding the orifice 35 of passage 33, the conical surface smoothly and with streamlines merging into the defining wall of the passage, which latter preferably is in the nature of a venturi, with the streamlined venturi restriction 36 at a point near said orifice.

The diaphragm 37 is in the nature of a bladder made of natural or synthetic rubber and is pre-formed, as by molding, so, when it is in equilibrium, it has the shape shown in solid lines (position D) in Fig. 3. The neck 39 and neck flange 40 of the bladder are tightly clamped in groove 22 and counterbore 23, respectively, thus not only positively fixing the upper end of the bladder to body shell 1(2), but also packing off the joint between sections 11 and 1 When in position D (that is, when the diaphragm is in equilibrium and thus in the shape it inherently assumes when detached from the shell) its upper portion 41 has an arcuate extent 42 which is complementary to and engages the upper shell wall 14.

Arcuate portion 42 terminates at 45, which lies approximately in plane A, and is connected to base portion 43 by a bend 44, annular as viewed in plan, whose lower edge 45' lies in plane G, and thus below plane A. Each portion of bend 44 is arcuate in vertical cross section, with the centers of the cross-sectional curvature lying approximately in plane A. Thus, when the diaphragm is in equilibrium, base portion 43 lies, in major extent at least, within the space bounded by said upper portion 42.

Starting from bend 44, the base portion 43 has a conical extent 46 which merges, by way of curved extent v7, into an uppermost, substantially horizontal and central extent 48. Embedded in this horizontal extent is a downwardly pointing conical valve stopper 49 which is rigid in nature and is keyed to the rubber at 50. The axes of stopper 45* and passage 33 are coincident with polar axis B. The rubber making up the diaphragm is continued integrally across the lower conical surface 51 of stopper 49 to provide a rubber facing 52 to seat on conical face 34 around orifice 35 when the bladder is in fully distended position, as represented by the dotted line position F, thus to close off passage 33 and prevent extrusion of the bladder into said passage.

Opening through cap section 12 and into the bladder, is a fluid flow passage 53, into which a valved fitting 54 is set. Gas such as compressed air or compressed nitro gen is introduced through fitting 54 to provide the pulsation absorbing or dampening agent when surges occur in the fluid admitted through passage 33 to chamber C be:

low the bladder. A gage 55 is in communication through passage 56 with the bladder interior, whereby the gas pressure within the bladder may be ascertained. Preferably, a guard 5'7 is bolted to cap section 12 to protect fitting 54 and gage 55, the guard having a gage-sighting opening 58.

The bladder is preferably prechargcd so it will be in position F, it having passed through position E in reach ing this position F. When in position E, the rubber of the diaphragm is nnstretched, except slightly at bend 44. In going from position E to position F, the body portion ofthe bladder is stretched but, since the bend 44 is relatively rigid, there will be a flattened, or return-bend effect 44 which will tend to stand the adjacent extent of the base portion away from Wall 15 to provide a space 59. Subsequently, an upward surge of fluid through passage 33 overcomes the previously predominant pressure in the bladder and thus unseats valve stopper 49 to admit fluid to chamber C below the bladder. When the gas pressure again becomes predominant and re-seats the stopper, fluid will be trapped in space 59 between return bend 44' and the seated stopper, and this trapped fluid will hold the aflected part of the bladder from contacting the shell wall, thus preventing abrasive wear on the bladder. The rubber facing 52 is adapted to make a tight seal whereby the trapping of the fluid is assured.

With the chamber C and bladder 38 shaped as shown and described, the diaphragm moves between its limits with a minimum of harmful folding, wrinkling and stretching. Contributing greatly to this eflect is the fact that the slant height X of the conical extent 46 of bladder base-portion 43 is made to be appreciably less than the radius Y of the bend annulus 44, Y also representing the radius of the base of the conical extent 46, when the bladder is in equilibrium (position D). It is also of decided advantage to pro-form the slant angle 64} of the conical extent so, when the diaphragm is in equilibrium, said angle is less than the angle 61 between the plane A and a chord 62 drawn from that plane to the upper end of arcuate extent 42. It has been found that an angle 6%) of is best suited to most purposes.

The venturi effect and the streamlining of passage 33 are extremely helpful in so directing the incoming stream of fluid as to distribute sediment evenly over the shell walls, thus preventing localization or pocketing of such sediment in such a manner that the diaphragm is locally displaced-for the localizing efliect would otherwise tend to cause undue wear of the bladder or to throw the stopper 49 out of line with passage 33, or both.

Various changes in design, structure and arrangement may be made Without departing from the spirit and scope of the appended claims.

I claim:

1. in a device of the character described, a body shell having upper and lower walls defining an interior chamher having the general shape-characteristics of an oblate spheroid arranged with its polar axis extending vertically, a rubber bladder within said chamber, the upper end of the bladder being detachably secured to said shell, said bladder being pie-formed so, when in equilibrium within the shell, it includes an upper portion snbstantialy complementary to the chamber defining wall above the equatorial axis of the chamber, and a base portion lying, in major extent at least, within the space bounded by said upper portion, said base portion including a base'down conical extent and an uppermost horizontal and central extent, the slant height of the conical extent being less than the radius of the base of the conical extent, there being a pair of fluid flow passages opening through the shell, one to the interior of the bladder and the other to the chamber at a point below the bladder.

2. A device as in claim 1; wherein said other port and said horizontal extent are coaxial and wherein the lower chamber-defining wall merges smoothly from a zone of curved cross section to a conical zone immediately surrounding said other passage, and a rigid, dowmvardly pointing conical stopper centrally carried by said horizontal extent, said stopper seating on the conical zone of said lower wall to close said other passage when the diaphragm is fully extended by predominant fluid pressure existing within the bladder.

3. A device as in claim 1; wherein the base of the conical extent lies in a :plane below the equatorial plane of the chamber. l

References Cited in the file of this patent 

